The objective of this project is to determine pertinent hydrodynamic characteristics related to flow in arterial stenoses, and to ascertain the role of these characteristics in the development of arterial disease associated with the presence of stenotic obstructions. By means of both in vitro and in vivo experiments the following characteristics, and their interrelationships, are being investigated: (1) stenosis geometry, (2) flow resistance, (3) localized regions of separated flow and turbulence. The in vitro tests involve model stenoses having well-defined geometries and operated under both steady and unsteady flow conditions. For the in vivo tests artificial stenoses are introduced in the carotid and femoral arteries of large mongrel dogs and measurements similar to those in the in vitro tests are made. Assessment of arterial wall damage will be made and correlated with flow characteristics.